The present invention relates to an ink jet recording apparatus, and a method of correcting calculation of a consumed amount of ink which is supplied from an ink cartridge loaded in the recording apparatus in order to exactly grasp a residual ink amount in the ink cartridge.
For example, in an ink jet recording apparatus provided for office or business use, an ink cartridge of large capacity must be used for dealing with a relatively large amount of printing. To cope with this, the ink cartridges of different color inks are loaded to a cartridge holder installed to the apparatus body. Subtanks are mounted on a carriage with a recording head mounted thereon. Ink is supplied from each ink cartridge to the associated subtank via an ink replenishing tube, and then is supplied to the recording head, from the subtank.
The ink cartridge used by the recording apparatus thus constructed is provided with an ink-end determinant for verifying as to whether or not each ink cartridge is in an ink-end state. An ink-end determinant is proposed which counts up the number of ink drops ejected from the recording head in accordance with print data and the number of ink drops ejected from the recording head based on a flushing operation, converts the count value into a consumed ink amount, and estimates an ink-end state based on the converted one.
In the ink-end determinant, the numbers of ink drops ejected are converted into the consumed ink amount. Accordingly, the converted values of the consumed ink amount are varied among the different recording apparatus. Usually, it is unavoidable that the weight value of the ink drop is varied by xc2x110% among the different recording apparatus. Accordingly, if the variation is shifted to an ink empty state, the machine judges that the ink cartridge is in an ink-end state, though the use recognizes that ink is still left in the ink cartridge. Such a situation should be avoided.
To avoid this, the weight of the ink drop is set based on a large weight of the ink drop within the variation of the weight values. Where the weight is so set, if the variation of weight value of the ink drop is shifted to the minimum weight, the machine will judge that the ink cartridge is in an ink-end state in a state that ink having an amount of 20% of the total ink capacity is left in the cartridge. Accordingly, the running cost is increased for the user. Since a relative large amount of ink is left in the used ink cartridge, a problem of disposing the residual ink in the ink cartridge additionally arises.
In recent years, with diversification of printing, the pigment-dispersed type ink tends to be employed. In this kind of ink, pigment precipitates into the solvent, so that a concentration of the residual ink is high. In this respect, there is a technical requirement of issuing an ink end sign immediately before the ink is used up in the ink cartridge. To meet such a requirement, the ink end must be judged highly accurately so as to leave a minimum amount of ink in the ink cartridge.
It is therefore an object of the present invention is to provide an ink jet recording apparatus which can judge an ink-end state with high accuracy by correcting calculation of a consumed ink amount in accordance with the individual difference of the recording apparatus, and a correction method which can attain the above.
In order to achieve the above object, according to the present invention, there is provided an ink jet recording apparatus, comprising:
a recording head, from which ink drops are ejected;
a cartridge holder, on which an ink cartridge for supplying ink to the recording head is detachably mounted;
a calculator, which performs calculation of an ink amount consumed by the recording head;
a first counter, which updates a residual ink amount in the mounted ink cartridge based on the consumed ink amount calculated by the calculator;
a monitor, which monitors an ink amount contained in the mounted ink cartridge to judge at least an ink-end state in which the ink amount in the ink cartridge is a predetermined amount or less; and
a corrector, which corrects the calculation in the calculator based on the residual ink amount indicated by the first counter, when the monitor judges that the mounted ink cartridge is in the ink-end state.
Preferably, the calculator multiplies a coefficient by the number of ink drops ejected from the recording head at least when a printing operation is performed and when a flushing operation is performed.
Here, it is preferable that the corrector corrects the coefficient. Further, it is preferable that the coefficient is managed in accordance with a weight of each ink drop.
Still further, it is preferable that the calculator performs the calculation every time when a cleaning operation of the recording head is performed.
Preferably, the ink jet recording apparatus further comprises a subtank, which stores ink replenished from the ink cartridge and supplies the ink to the recording head. Here, the monitor judges the ink-end state when a predetermined amount of ink is not replenished from the ink cartridge to the subtank, even though a predetermined time period has elapsed since the ink replenishment is started.
Here, the ink cartridge and the subtank are connected via a replenishing passage provided with a valve. The subtank includes a detector which detects an ink amount contained in the subtank. The valve is opened when the consumed ink amount calculated by the calculator reaches a predetermined value. The valve is closed when the detector detects an ink-full state in which the ink replenished in the subtank reaches a predetermined amount.
Further, it is preferable that the detector includes a float member which floats on the ink contained in the subtank, and a signal generator which generates an electric signal varied in accordance with a position of the float member in the subtank.
Here, it is preferable that the monitor includes a timer which starts clocking when the valve is opened. The monitor judges the ink-end state when the ink-full state is not detected by the detector even though the timer clocks a predetermined time period.
Preferably, the ink-end state judged by the monitor is effected only when the updated residual ink amount of the first counter is a predetermined value or less. Here, the monitor refers to the residual ink amount indicated by the first counter when the apparatus is activated, when the ink cartridge is replaced, and when a printing operation is paused to feed a next recording sheet. Here, operations of the recording apparatus is stopped when the monitor judges the ink-end state.
Preferably, the ink jet recording apparatus further comprises an air compressor. Here, the ink cartridge includes an air-tight casing, a flexible ink pack containing ink therein, which is accommodated within the casing. Air compressed by the air compressor is applied to a space defined between the casing and the ink pack so that the ink pack is contracted in accordance with the ink replenishment to the subtank.
Here, it is preferable that the monitor includes a plate member provided on the ink pack and a switch member which is operated by the plate member in accordance with the contraction of the ink pack.
Alternatively, it is preferable that the monitor includes a transparent part formed on at least a lower portion of the ink cartridge, at least one pair of a light source and a photo sensor, which are opposed to each other through the transparent part. Here, the monitor judges the ink-end state when an ink level in the ink cartridge lowers an optical path ranging from the light source to the photo sensor.
Alternatively, it is preferable that the monitor includes a prism member formed on at least a lower part of the ink cartridge. The monitor judges the ink-end state based on a difference between a first critical angle of total reflection defined by refractive indices of the ink in the ink cartridge and a material of the prism member, and a second critical angle of total reflection defined by refractive indices of the material of the prism member and atmosphere. Here, the monitor includes at least one pair of a light source which emits a light beam toward the prism member and a photo sensor which detects the light beam reflected by the prism member. The monitor judges the ink-end state when the photo sensor detects the light beam reflected by the prism member.
Alternatively, it is preferable that the monitor includes at least one pair of electrode terminals provided in at least a lower portion of the ink cartridge while extending inside of the ink cartridge and a detection circuit which detects a resistance between the electrode terminals. Here, the monitor judges the ink-end state when the detection circuit detects a drop of the resistance.
Preferably, the ink jet recording apparatus further comprises:
a subtank, which stores ink replenished from the ink cartridge and supplies the ink to the recording head;
a detector, which detects an ink amount contained in the subtank;
a second counter, which updates an ink amount consumed by the recording head based on the consumed ink amount calculated by the calculator,
wherein the corrector corrects the calculation in the calculator based on the consumed ink amount indicated by the second counter, when the detector detects that the ink amount in the subtank is a predetermined amount or less.
According to the present invention, there is also provided a method of correcting calculation for an ink amount consumed in a recording head incorporated in an ink jet recording apparatus, the step comprising the steps of:
providing an ink tank which supplies ink to the recording head;
providing a counter which indicates a residual ink amount in the ink tank;
calculating an ink amount consumed by the recording head;
updating the residual ink amount indicated by the counter, based on the calculated consumed ink amount;
monitoring a residual ink amount in the ink tank independently from the counter; and
correcting the way of calculation, based on the updated residual ink amount of the counter, when the monitored residual ink amount is predetermined amount or less.
Here, it is preferable that the calculation is performed by multiplying a coefficient by the number of ink drops ejected from the recording head at least when a printing operation is performed and when a flushing operation is performed. The coefficient is corrected in the correcting step.
According to the above configurations, when the monitor judges that the ink cartridge is in the ink-end state, a count value of the first counter is referred to. The way of calculation in the calculator is corrected according to the referred count value of the first counter.
When the referred count value of the first counter indicates that the residual ink amount is larger than a predetermined amount, the coefficient to be multiplied by the number of ink drops ejected from the recording head is corrected to be large, viz., the weight of the ink drop is corrected to be large. As a result, a counting rate of the calculating value in the consumed ink amount calculator is increased.
When the referred count value of the first counter indicates that the residual ink amount is smaller than the predetermined value, the correction process is performed in the contrary manner to that in the above case. As a result, a counting rate of the calculating value in the consumed ink amount calculator is decreased.
If the coefficient correcting process is repeatedly executed for several times of the replacement of the ink cartridge, the judging accuracy may be improved. With this, variations of the judging results of the different recording apparatus are made small.
According to the present invention, there is also provided an ink jet recording apparatus, comprising:
a recording head, from which ink drops are ejected;
a cartridge holder, on which an ink cartridge for supplying ink to the recording head is detachably mounted;
a subtank, which stores ink replenished from the ink cartridge and supplies the ink to the recording head;
a detector, which detects an ink amount contained in the subtank;
a calculator, which performs calculation of an ink amount consumed by the recording head;
a counter, which updates a consumed ink amount based on the consumed ink amount calculated by the calculator; and
a corrector, which corrects the calculation in the calculator based on the consumed ink amount indicated by the counter, when the detector detects that the ink amount in the subtank is a predetermined amount or less.
According to the present invention, there is also provided a method of correcting calculation for an ink amount consumed in a recording head incorporated in an ink jet recording apparatus, the step comprising the steps of:
providing an ink tank which supplies ink to the recording head;
providing a counter which indicates an ink amount consumed by the recording head;
calculating an ink amount consumed by the recording head;
updating the consumed ink amount indicated by the counter, based on the calculated consumed ink amount;
monitoring a residual ink amount in the ink tank independently from the counter; and
correcting the way of calculation, based on the updated consumed ink amount of the counter, when the monitored residual ink amount is predetermined amount or less.
Also in these configurations, the similar advantages as explained the above can be attained. In addition, since the corrector corrects the way of calculation in the calculator based on the count value of the counter when the detector detects that the amount of ink in the subtank is a predetermined amount or less, the calculation may effectively be corrected even when the ink cartridge is being used.